Semiconductor devices with ball strength improvement

ABSTRACT

A semiconductor device includes a contact region over a substrate. The semiconductor device further includes a metal pad over the contact region. Additionally, the semiconductor device includes a post passivation interconnect (PPI) line over the metal pad, where the PPI line is in contact with the metal pad. Furthermore, the semiconductor device includes an under-bump-metallurgy (UBM) layer over the PPI line. Moreover, the semiconductor device includes a plurality of solder balls over the UBM layer, the plurality of solder balls being arranged at some, but not all, intersections of a number of columns and rows of a ball pattern.

PRIORITY CLAIM

The present application is a divisional of U.S. application Ser. No.13/291,550, filed Nov. 8, 2011, which is incorporated by referenceherein in its entirety.

TECHNICAL FIELD

The present disclosure relates to semiconductor devices with ballstrength improvement.

BACKGROUND

The recent trend in miniaturizing integrated circuits (IC or chip) haslead to various types of IC packages, such as chip scale packages (CSP).

For example, in a wire-bonded CSP, a chip is electrically connected toan underlying substrate by bonding wires. Such a configuration requiresa size increase both in height to accommodate wire loops and in widthand/or length to accommodate wire bonding pads. To further reduce thepackage size, flip-chip CSPs have been proposed.

In a flip-chip CSP, a chip is electrically connected to an underlyingsubstrate not by wires but by solder bumps.

In such a flip-chip CSP, if there is a mismatch in the coefficients ofthermal expansion (CTE) between the chip and the substrate, for example,if the CTE of the substrate is greater than that of the chip, thesubstrate contracts at a greater rate than the chip when the temperatureis reduced, e.g., after a solder-reflowing process. As a result, warpageoccurs to the CSP which, in turn, causes product reliability and/orproduction yield issues.

To prevent warpage, it has been proposed to add an underfill materialbetween the chip and the substrate to “lock” the chip to the substrate.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more embodiments are illustrated by way of example, and not bylimitation, in the figures of the accompanying drawings, whereinelements having the same reference numeral designations represent likeelements throughout. The drawings are not to scale, unless otherwisedisclosed.

FIG. 1 is a schematic plan view of a ball pattern.

FIGS. 2A-2C, 3 and 4 are schematic plan views of some regions of a ballpattern.

FIG. 5 is a flow chart of a method in accordance with some embodiments.

FIGS. 6A and 6B are schematic plan views of a ball pattern and amodified ball pattern in accordance with some embodiments, respectively.

FIGS. 7A and 7B are cross-section views taken along line A-A′ in FIG. 6Aand line B-B′ in FIG. 6B, respectively.

FIG. 8 is a flow chart of a method in accordance with some embodiments.

FIGS. 9A and 9B are schematic plan views of a ball pattern and amodified ball pattern in accordance with some embodiments, respectively.

FIG. 10 is a flow chart of a method in accordance with some embodiments.

FIGS. 11A and 11B are schematic plan views of a ball pattern and amodified ball pattern in accordance with some embodiments, respectively.

FIG. 12 is a flow chart of a method in accordance with some embodiments.

FIG. 13 is a schematic cross-section view of a chip scale package (CSP)in accordance with some embodiments.

DETAILED DESCRIPTION

It is to be understood that the following disclosure provides manydifferent embodiments or examples, for implementing different featuresof various embodiments. Specific examples of components and arrangementsare described below to simplify the present disclosure. The inventiveconcept may, however, be embodied in many different forms and should notbe construed as being limited to the embodiments set forth herein;rather, these embodiments are provided so that this description will bethorough and complete, and will fully convey the inventive concept tothose of ordinary skill in the art. It will be apparent, however, thatone or more embodiments may be practiced without these specific details.

In the drawings, the thickness and width of layers and regions areexaggerated for clarity. Like reference numerals in the drawings denotelike elements. The elements and regions illustrated in the figures areschematic in nature, and thus relative sizes or intervals illustrated inthe figures are not intended to limit the scope of the inventiveconcept.

The inventors have recognized that an arrangement of solder bumps orsolder balls for electrical connectivity of a chip or a chip package toa substrate or another component is often configured with primaryconsiderations given to the chip's operation, rather than mechanicalstrength. In some cases, the solder bumps or solder balls are notuniformly distributed across the surface of the chip or chip package.Some uneven distributions of solder bumps or solder balls generate ahigher stress at some solder bumps or solder balls than at other solderbumps or balls. As a result, issues such as ball/bump crack or diechipping are likely to occur.

In some embodiments, a ball pattern of balls to be formed for a chip orchip package is modified so that at least a region of the ball patternincludes no isolated ball, as used herein, for improved ball strength.In some embodiments, such modification includes moving and/or adding oneor more balls so that an isolated ball has at least two neighboringballs and is no longer considered isolated. In some embodiments, theisolated ball, for which the modification is performed, is a corner ballof the ball pattern.

As used herein, a “semiconductor device” is a chip or a chip packagecontaining therein at least one chip.

An example of a semiconductor device is a bare chip or die (asexemplarily shown at 102 in FIG. 13). Another example of a semiconductordevice is a chip package (as exemplarily shown at 1300 in FIG. 13) whichincludes, in addition to at least one chip (such as 102 in FIG. 13), acarrier or substrate (such as 104 in FIG. 13) on which the at least onechip is mounted. Yet another example of a semiconductor device is astack of chips one on top another. A further example of a semiconductordevice is a multi-chip package that includes more than one chip. In someembodiments, a chip package further includes an encapsulant (asexemplarily shown at 108 in FIG. 13) embedding therein the chip orchips.

As used herein, a “connection ball” is a conductive bump or balldeposited on a surface of a semiconductor device for electricallyconnecting the chip(s) of the semiconductor device to at least oneexternal component or device. The connection ball also functions tophysically connect the semiconductor device to the external component ordevice. However, the primary function of the connection ball is totransmit electrical signals, e.g., power, ground, or data, to/from thesemiconductor device.

An example of a connection ball is a solder bump (as exemplarily shownat 106 in FIG. 13) on a surface of a chip (as exemplarily shown at 102in FIG. 13) for electrically connecting the chip to at least oneexternal component or device (e.g., a substrate or carrier asexemplarily shown at 104 in FIG. 13). Another example of a connectionball is a solder ball (as exemplarily shown at 110 in FIG. 13) on asurface of a chip package (as exemplarily shown at 1300 in FIG. 13) forelectrically connecting the chip in the chip package to at least oneexternal component or device (not shown).

As used herein, a “dummy ball” is a bump or ball deposited on the samesurface of a semiconductor device on which connection balls of thesemiconductor device are provided for electrically connecting thechip(s) of the semiconductor device to at least one external componentor device; however, the dummy ball is primarily for physicallyconnecting the semiconductor device to the at least one externalcomponent or device.

In some embodiments, the dummy ball provides no electrical connectionbetween the semiconductor device and the external component or device.In an example, the dummy ball is not in electrical connection with thesemiconductor device. In a further example, the dummy ball is inelectrical connection with the semiconductor device, but not inelectrical connection with the external component or device.

In some embodiments, the dummy ball provides an electrical connectionbetween the semiconductor device and the external component or device.However, such electrical connection does not affect the intendedoperation or functionality of the semiconductor device. For example, thedummy ball provides an electrical connection for a ground or powersupply voltage between the semiconductor device and the externalcomponent or device, in addition to one or more other ground or powerconnections already provided by one or more connection balls of thesemiconductor device.

As used herein, “connection ball” and “dummy ball” are commonly referredto as “ball” unless otherwise specified.

FIG. 1 is a schematic plan view of a ball pattern 300 of a semiconductordevice (not shown). The ball pattern 300 includes a plurality ofconnection balls 306 for the semiconductor device. The ball pattern 300includes a plurality of columns 321 (exemplarily identified by verticalarrows in FIG. 1) and rows 323 (exemplarily identified by horizontalarrows in FIG. 1) which cross or intersect each other at a plurality ofintersections 325. For the sake of simplicity, only one intersection 325is indicated in FIG. 1 at the intersection of a column 321′ and a row323′. In some embodiments, the columns and rows are perpendicular toeach other as exemplarily illustrated in FIG. 1. In some embodiments,the columns and rows are not perpendicular, e.g., they intersect at anangle greater than 90 degrees or less than 90 degrees.

The connection balls 306 are each arranged at one of the intersections325. As noted above, the physical arrangement of the connection balls306 is configured with primary consideration given to the semiconductordevice's operation, rather than mechanical strength. As such, theconnection balls 306 are often unevenly distributed as exemplarilyillustrated in FIG. 1. Such an uneven distribution of balls generates ahigher stress at some balls than at other balls. As a result, issuessuch as ball crack or die chipping (during backside grinding) are likelyto occur.

The inventors have found that isolated balls are likely causes ofdefects, such as ball crack or die chipping, especially when suchisolated balls are corner balls, i.e., balls that are located at thecorners of the ball pattern, as exemplarily illustrated at 306 c in FIG.1.

As used herein, an “isolated ball” is a ball that has no or only oneneighboring ball.

As used herein, a “neighboring ball” of a specific ball is a ballimmediately adjacent the specific ball in the same column or row as thespecific ball.

For example, as exemplarily illustrated in FIG. 1, a specific ball 306 shas three neighboring balls 306 n each of which is immediately adjacentto and on the same column or row as the specific ball 306 s. A ball 306z, which is adjacent the specific ball 306 s but is not on the samecolumn or row as the specific ball 306 s, is not a neighboring ball,i.e., diagonally-adjacent balls are not considered neighboring balls.

Several isolated balls 306 i are identified (by small circles) in theball pattern 300. As exemplarily illustrated in FIG. 1, each of theisolated balls 306 i has at most one neighboring ball. Some of thecorner balls 306 c are also isolated balls which are especially likelyto suffer from defects, such as ball crack or void, etc.

FIGS. 2A-2C and 3-4 are schematic plan views of possible corner regions400A-400E, respectively, of a ball pattern, such as the ball pattern300. As exemplarily illustrated in FIGS. 2A-2C and 3-4, a corner regionis a region that includes a corner of the ball pattern. A corner ball isnot necessarily arranged at a corner of the ball pattern for a regioncontaining the corner to be considered a corner region. For example, asexemplarily illustrated in FIG. 3, the corner 325 c of the ball patternis empty, yet the region 400D containing the empty corner 325 c is stillconsidered a corner region.

The corner balls 306 c of the corner regions 400A and 400B are isolatedballs each having only one neighboring ball 306 n. The corner ball 306 cof the corner region 400C is also an isolated ball having no neighboringball. The corner region 400D has no corner ball. Further, each and everyball in the corner region 400D has at least two neighboring balls. Thecorner region 400E has the corner ball 306 c which is not an isolatedball. Further, each and every ball in the corner region 400E has atleast two neighboring balls.

The inventors have found that the mean fatigue life of a semiconductordevice including a ball pattern having a corner region with an isolatedball (such as the corner regions 400A-400C) is about 15% to 20% lowerthan the mean fatigue life of a semiconductor device including a ballpattern having corner regions with no isolated balls (such as the cornerregions 400D-400E). In other words, a corner region with no isolatedballs (such as the corner regions 400D-400E) provides improved ballstrength over a corner region with an isolated ball (such as the cornerregions 400A-400C). This is also true for any other region (notnecessarily a corner region) and/or for any ball (not necessarily acorner ball) in the ball pattern. For example, the ball strength of a(non-corner) region including an isolated ball 306 w (which is not acorner ball) in FIG. 1 would be improved if the region included noisolated balls.

Accordingly, in accordance with some embodiments, an arrangement ofballs in a region of a ball pattern is modified so that the regionincludes no isolated balls. FIG. 5 is a flow chart of a method 500 inaccordance with such embodiments.

At step 501, a ball pattern of a plurality of connection balls to beformed as electrical connections for a semiconductor device is received.The received ball pattern includes a region with an isolated ball (e.g.,the corner region 400A).

As step 503, an arrangement of balls in the region 400A is modified sothat the region no longer includes isolated balls. For example, theregion 400A, 400B or 400C is modified in some embodiments to become theregion 400D or 400E with no isolated balls.

At step 505, the semiconductor device is manufactured with the modifiedball pattern. Any manufacturing process suitable for fabrication ofsemiconductor devices is applicable. An exemplary process will bedescribed later with respect to FIGS. 7A-7B.

In some embodiments, the region to be modified at step 503 is a cornerregion of the ball pattern. In further embodiments, the region to bemodified at step 503 includes some or all corner regions of the ballpattern. In yet further embodiments, the region to be modified at step503 is the entire ball pattern.

In step 503, one potential modification includes moving the isolatedball to an empty intersection, so that every ball in the region beingmodified has at least two neighboring balls.

For example, the isolated ball (e.g., the corner ball 306 c) in region400A which is also a connection ball is moved to an empty intersection(e.g., 325 e in FIG. 2A). The region 400A will then become the region400D in which every ball has at least two neighboring balls. The movedball (e.g., 306 m in FIG. 3) remains a connection ball to ensure properor intended operation or functionality of the semiconductor device.Rerouting of one or more conductive layers of the semiconductor deviceis performed in some embodiments to provide a proper electricalconnection to/from the moved ball 306 m.

Similarly, if the region with an isolated ball is the region 400B, it ismodified in some embodiments to become the region 400D by moving theisolated ball (e.g., the corner ball 306 c in region 400B) to an emptyintersection (e.g., 325 e in FIG. 2B). Likewise, if the region with anisolated ball is the region 400C, it is modified in some embodiments tobecome the region 400D by moving the isolated ball (e.g., the cornerball 306 c in region 400C) to an empty intersection (e.g., either of thetwo empty intersections 325 e in FIG. 2C).

In some embodiments, the isolated ball is moved completely out of theregion being modified. For example, the isolated ball (e.g., the cornerball 306 c) in region 400C is completely moved out of the region 400C,making the modified region free of isolated balls.

In step 503, another potential modification includes adding a dummy ballto an empty intersection so that every ball in the region being modifiedhas at least two neighboring balls. In some embodiments, the adding ofdummy ball is performed in place of or in addition to the moving ofconnection ball as described above.

In some embodiments, dummy balls are added to all empty intersections inthe region to be modified (e.g., any of the regions 400A-400C). In otherwords, the modification includes populating every empty intersection inthe region being modified with a dummy ball. As a result, the region400E is obtained in which every ball has at least two neighboring balls.

However, dummy balls are not necessarily added to all emptyintersections in the region to be modified, provided that every ball inthe modified region has at least two neighboring balls, as exemplarilydisclosed herein below.

FIGS. 6A and 6B are schematic plan views of a ball pattern 600A and amodified ball pattern 600B in accordance with some embodiments,respectively. FIG. 8 is a flow chart of a method 800 in accordance withsome embodiments. The ball patterns of FIGS. 6A-6B will be used forillustration purposes with respect to the description of FIG. 8.

At step 801, a ball pattern (such as the ball pattern 600A in FIG. 6A)of a plurality of connection balls 306 to be formed as electricalconnections for a semiconductor device is received. The connection balls306 are arranged at some, but not all, intersections of the columns androws (not numbered) of the ball pattern 600A. Thus, some intersectionsremain empty as exemplarily illustrated at 325 e in FIG. 6A.

As step 802, at least one of the corner regions 651-654 (FIG. 6A) isanalyzed to identify any isolated ball existing in the corner region. Asdiscussed before, an isolated ball is a ball that has at most oneneighboring ball. For example, in the exemplary ball pattern 600A inFIG. 6A, when the corner region 651 is analyzed, two isolated balls 306i are identified one of which is a corner ball 306 c.

In some embodiments, the analysis is performed manually, e.g., byvisually examining the layout of the received ball pattern 600A. In someembodiments, the analysis is performed by a computer system hardwired orprogrammed to identify isolated balls. For example, the computer system,e.g., a general purpose computer system, is configured to count, foreach ball, the number of neighboring balls immediately adjacent to andon the same column or row as the ball in question. If the counted numberof neighboring balls is one or zero, the ball in question is flagged asan isolated ball.

As step 803, the at least one corner region, e.g., 651, is modified byadding one or more dummy balls each to an empty intersection adjacentthe identified isolated ball, e.g., the corner ball 306 c in the cornerregion 651, so that the ball has two or more neighboring balls and is nolonger considered isolated. Similar to step 802, the dummy ball additionis performed either manually or by way of a computer system.

For example, at least one dummy ball 306 d 1 is added to an emptyintersection adjacent the corner balls 306 c (which is identified atstep 802 as an isolated ball) in the corner region 651, as exemplarilyillustrated in FIG. 6B. Thus, the corner ball 306 c in the corner region651 in the modified ball pattern 600B is no longer considered isolated,as it now has two neighboring balls, one neighboring ball being theadded dummy ball 306 d 1, the other neighboring ball being theconnection ball 306 k immediately below the corner ball 306 c in thesame column. Step 803 in accordance with some embodiments which arearranged to improve corner ball strength in the analyzed corner regionis terminated here.

In some embodiments, step 803 is performed not only to improve cornerball strength, but also to improve ball strength at other connectionballs in the analyzed corner region. For example, the corner region 651also includes another connection ball 306 k which has also beenidentified as an isolated ball. Thus, at least another dummy ball 306 d2 is added to an empty intersection adjacent the isolated ball 306 k, asexemplarily illustrated in FIG. 6B. Thus, the ball 306 k in the modifiedball pattern 600B is no longer considered isolated, as it now has twoneighboring balls, one neighboring ball being the added dummy ball 306 d2, the other neighboring ball being the corner ball 306 c immediatelyabove the ball 306 k in the same column. Step 803 in accordance withsome embodiments which are arranged to improve connection ball strengthin the analyzed corner region is terminated here.

In some embodiments, step 803 is performed not only to improveconnection ball strength, but also to improve dummy ball strength in theanalyzed corner region. For example, as seen in FIG. 6B, when the dummyball 306 d 1 is added, it is an isolated ball having only oneneighboring ball being the corner ball 306 c. If the semiconductordevice is manufactured with such an isolated dummy ball, the isolateddummy ball is subject to increased stress and is prone to defects suchas ball crack. Since the isolated dummy ball is not required to provideintended operation or functionality for the semiconductor device, acrack, if such occurs, is unlikely to affect the semiconductor device'soperation or functionality. Therefore, in some situations, isolateddummy balls are acceptable in the modified ball pattern.

However, in situations where a crack even in an isolated dummy balland/or die chipping related to isolated dummy balls is/are notdesirable, one or more further dummy balls are added to ensure that, inthe analyzed corner region, no isolated balls (including both connectionand dummy balls) exist. For example, in the modified ball pattern 600Bof FIG. 6, a further dummy ball 306 d 3 is added to an emptyintersection adjacent the isolated dummy ball 306 d 1, so that the dummyball 306 d 1 has at least two neighboring balls and is no longerconsidered to be an isolated ball.

The newly added dummy ball 306 d 3 is analyzed in some embodiments todetermine whether the newly added dummy ball is an isolated ball. If theanswer is positive, another dummy ball is added to an empty intersectionadjacent the isolated dummy ball 306 d 3, so that the dummy ball 306 d 3has at least two neighboring balls and is no longer considered anisolated ball. The process repeated until every ball (no matter whetherit is a connection ball or a dummy ball) in the analyzed corner regionhas two or more neighboring balls. The neighboring balls need not belocated in the analyzed corner region. For example, the dummy ball 306 d3 in FIG. 6B has a neighboring ball 306 t which is outside the analyzedcorner region 651. Step 803 in accordance with some embodiments whichare arranged to improve both connection and dummy ball strength in theanalyzed corner region is terminated here.

At step 805, the semiconductor device is manufactured with the modifiedball pattern. Any manufacturing process suitable for fabrication ofsemiconductor devices is applicable. An exemplary process will now beexemplarily described with respect to FIGS. 7A-7B which arecross-section views taken along line A-A′ in FIG. 6A and line B-B′ inFIG. 6B, respectively.

As can be seen in FIG. 7A, a semiconductor device 700 includes asubstrate 710 which is a semiconductor substrate with integratedcircuits formed therein and/or thereon. The substrate 710 includes, butis not limited to, bulk silicon, a semiconductor wafer, asilicon-on-insulator (SOI) substrate, or a silicon germanium substrate.Other semiconductor materials including group III, group IV, and group Velements are used in some embodiments. The substrate 710, in someembodiments, further comprises a plurality of isolation features (notshown), such as shallow trench isolation (STI) features or localoxidation of silicon (LOCOS) features. The isolation features define andisolate various microelectronic elements (not shown). Examples of suchvarious microelectronic elements formed in the substrate 710 inaccordance with some embodiments include transistors (e.g., metal oxidesemiconductor field effect transistors (MOSFET), complementary metaloxide semiconductor (CMOS) transistors, bipolar junction transistors(BJT), high voltage transistors, high frequency transistors, p-channeland/or n-channel field effect transistors (PFETs/NFETs), etc.);resistors; diodes; capacitors; inductors; fuses; and other suitableelements. Various processes are performed to form the variousmicroelectronic elements including deposition, etching, implantation,photolithography, annealing, and other suitable processes. Themicroelectronic elements are interconnected to form the integratedcircuit device, such as a logic device, memory device (e.g., SRAM), RFdevice, input/output (I/O) device, system-on-chip (SoC) device,combinations thereof, and other suitable types of devices.

The substrate 710 further includes, in some embodiments, inter-layerdielectric layers and a metallization structure overlying the integratedcircuits. The inter-layer dielectric layers in the metallizationstructure include low-k dielectric materials, un-doped silicate glass(USG), silicon nitride, silicon oxynitride, or other commonly usedmaterials. The dielectric constants (k value) of the low-k dielectricmaterials is, in some embodiments, less than about 3.9, or less thanabout 2.8. Metal lines in the metallization structure are, in someembodiments, formed of copper or copper alloys. One skilled in the artwill realize the formation details of the metallization layers.

A contact region 712 is a top metallization layer formed in a top-levelinter-layer dielectric layer, which is a portion of conductive routesand has an exposed surface treated by a planarization process, such aschemical mechanical polishing (CMP), if necessary. Suitable materialsfor the contact region 712 include, but are not limited to, for example,copper (Cu), aluminum (Al), AlCu, copper alloy, or other conductivematerials. In one embodiment, the contact region 712 includes a metalpad 713 (e.g., Al), which is, in some embodiments, used in the bondingprocess to connect the integrated circuits in the respective chip toexternal features.

A passivation layer 714 is formed on the substrate 710 and patterned toform an opening 715 exposing a portion of the metal pad 713 for allowingsubsequent post passivation interconnect processes. In one embodiment,the passivation layer 714 is formed of a non-organic material selectedfrom un-doped silicate glass (USG), silicon nitride, silicon oxynitride,silicon oxide, and combinations thereof. In another embodiment, thepassivation layer 714 is formed of a polymer layer, such as an epoxy,polyimide, benzocyclobutene (BCB), polybenzoxazole (PBO), and the like,although other relatively soft, often organic, dielectric materials arealso usable.

A post passivation interconnect (PPI) process is then performed on thepassivation layer 714. In some embodiments, an adhesion layer (notshown) and a seed layer (not shown) are formed on the passivation layer714 to line the sidewalls and bottom of the opening 715. The adhesionlayer, also referred to as a glue layer, is blanket formed, covering thepassivation layer 714 and the sidewalls and the bottom of the opening715. The adhesion layer includes commonly used barrier materials such astitanium, titanium nitride, tantalum, tantalum nitride, and combinationsthereof, and is formed using physical vapor deposition, sputtering, orthe like. The adhesion layer helps to improve the adhesion of thesubsequently formed conductive lines onto passivation layer 714. Theseed layer is blanket formed on the adhesion layer. The materials of theseed layer include aluminum, aluminum, alloys copper, copper alloys,silver, gold, aluminum, and combinations thereof. In an embodiment, theseed layer is formed of sputtering. In other embodiments, other commonlyused methods such as physical vapor deposition or electroless platingare used.

A post passivation interconnect (PPI) line 718 is formed on the adhesionlayer and seed layer (if used) to fill the opening 715. Using a mask anda photolithography process, a conductive material fills the opening 715of the passivation layer 714 and an opening of the mask, followed byremoving the mask and any exposed portions of the adhesion layer andseed layer. The removal includes a wet etching process or a dry etchingprocess. In one embodiment, the removal includes an isotropic wetetching using an ammonia-based acid, which is, in some embodiments, aflash etching with a short duration.

The conductive material filling the opening 715 serves as the PPI line718. The PPI line 718 includes, but is not limited to, for example,copper, aluminum, copper alloy, or other conductive materials. The PPIline 718 further includes, in some embodiments, a nickel-containinglayer (not shown) on the top of a copper-containing layer. The PPIformation methods include plating, electroless plating, sputtering,chemical vapor deposition methods, and the like. The PPI line 718connects the contact region 712 to bump features. The PPI line 718 alsofunctions, in some embodiments, as power lines, re-distribution lines(RDL), inductors, capacitors or any passive components. The PPI line 718in some embodiments has a thickness less than about 30 μm, for example,between about 2 μm and about 25 μm.

A dielectric layer (not shown), also referred to as an isolation layeror a passivation layer, is formed in some embodiments on the exposedpassivation layer 714 and the PPI line 718. The dielectric layer isformed of dielectric materials such as silicon nitride, silicon carbide,silicon oxynitride or other applicable materials. The formation methodsinclude plasma enhance chemical vapor deposition (PECVD) or othercommonly used CVD methods.

A polymer layer 722 is formed on the dielectric layer. Lithographytechnology and etching processes such as a dry etch and/or a wet etchprocess, are then performed to pattern the polymer layer 722, thus anopening 723 is formed to pass through the polymer layer 722 and expose aportion of the PPI line 718 for allowing subsequent bump process. Thepolymer layer 722, as the name suggests, is formed of a polymer, such asan epoxy, polyimide, benzocyclobutene (BCB), polybenzoxazole (PBO), andthe like, although other relatively soft, often organic, dielectricmaterials can also be used. In one embodiment, the polymer layer 722 isa polyimide layer. In another embodiment, the polymer layer 722 is apolybenzoxazole (PBO) layer. The polymer layer 722 is soft, and hencehas the function of reducing inherent stresses on respective substrate.In addition, the polymer layer 722 is easily formed to a thickness oftens of microns.

An under-bump-metallurgy (UBM) layer 724 that includes, in someembodiments, a diffusion barrier layer and a seed layer are formed. TheUBM layer 724 is formed on the polymer layer 722 and the exposed portionof the PPI line 718, and lines the sidewalls and bottom of the opening723. The diffusion barrier layer, also referred to as a glue layer, isformed to cover the sidewalls and the bottom of the opening 723. Thediffusion barrier layer is, in some embodiments, formed of tantalumnitride, titanium nitride, tantalum, titanium, or the like. Theformation methods include physical vapor deposition (PVD) or sputtering.The seed layer is, in some embodiments, a copper seed layer formed onthe diffusion barrier layer. The seed layer is, in some embodiments,formed of copper alloys that include silver, chromium, nickel, tin,gold, and combinations thereof. In one embodiment, the UBM layer 724includes a diffusion barrier layer formed of Ti and a seed layer formedof Cu.

A mask layer (not shown) is provided on the UBM layer 724 and patternedfor exposing a portion of the UBM layer 724 for bump formation. Aconductive material with solder wettability, such as SnAg, or otherlead-free or lead-containing solder materials, is deposited on theexposed portion, thereby forming a bump (or ball) 306 in contact withthe underlying UBM layer 724. The bump 306 defines a connection ball forthe semiconductor device 700.

The dummy ball 306 d (FIG. 7B) is formed, in some embodiments, in asimilar manner to connection ball 306, except that dummy ball 306 d isnot formed in electrical connection with the IC(s) formed in or on thesubstrate 710. In some embodiments, the dummy ball 306 d is formed onthe polymer layer 722 with or without an intervening layer which has thesame material as and is formed simultaneously with the UBM layer 724. Insome embodiments, the dummy ball 306 d has the same material as and isformed simultaneously with the connection ball 306.

The semiconductor device 700 with the connection ball(s) 306 and one ormore dummy ball(s) 306 d formed thereon is flipped and bonded to anunderlying substrate (or another chip) by reflowing the balls 306 and306 d. The resulting structure is optionally encapsulated and solderballs are formed as disclosed herein with respect to FIG. 13.

In some embodiments, step 803 is performed to ensure that every cornerball of the modified ball pattern has two neighboring balls. For thispurpose, as exemplarily illustrated in FIG. 6B, in addition to the dummyball 306 d 1 added to the corner region 651, two dummy balls are addedto the corner region 652 and one dummy ball (not numbered) is added tothe corner region 653. The corner region 654 needs no modification as itis already free of isolated balls.

In some embodiments, step 803 is performed to ensure that every ball inat least one corner region of the modified ball pattern has two or moreneighboring balls. For example and as disclosed above, dummy balls 306 d2 and 306 d 3 are added to ensure that every ball in the corner region651 has at least two neighboring balls.

In some embodiments, step 803 is performed to ensure that every ball inall corner regions, e.g., 651, 652, 653 and 654, of the modified ballpattern has two or more neighboring balls.

In some embodiments, step 803 is performed only for the corner regions,e.g., 651, 652, 653 and 654, to ensure that every ball in all cornerregions of the modified ball pattern has two or more neighboring balls.For example, the modified ball pattern 600B in FIG. 6B includes noisolated balls in all corner regions, but still includes one or moreisolated ball, e.g., 306 g in FIG. 6B, outside the corner regions.

For the purpose of improving ball strength in one or more cornerregions, a corner region is defined to be a region that contains acorner of the ball pattern and has dimensions which are about one thirdof a respective dimension of the ball pattern. For example, assume thatthe ball pattern (600B in FIG. 6) has a length B and a width B′, alength A and a width A′ of each corner region satisfy the followingrelationships: A≦⅓*B and A′≦⅓*B′.

FIGS. 9A and 9B are schematic plan views of a ball pattern 900A and amodified ball pattern 900B in accordance with some embodiments,respectively. FIG. 10 is a flow chart of a method 1000 in accordancewith some embodiments. The ball patterns of FIGS. 9A-9B will be used forillustration purposes with respect to the description of FIG. 10.

At step 1001, a ball pattern (such as the ball pattern 900A in FIG. 9A)of a plurality of connection balls 306 to be formed as electricalconnections for a semiconductor device is received. The connection balls306 are arranged at some, but not all, intersections of the columns androws (not numbered) of the ball pattern 900A. Thus, some intersectionsremain empty as exemplarily illustrated at 325 e in FIG. 9A.

At step 1002, the received ball pattern 900A is analyzed to identify anyisolated ball. The analysis is performed in a manner similar to thatdescribed with respect to step 802.

At step 1003, the ball pattern 900A is modified by adding one or moredummy balls each to an empty intersection adjacent one of the identifiedisolated balls, so as to ensure that every ball in the modified ballpattern, including all connection and dummy balls, has two or moreneighboring balls. The result is exemplarily illustrated in FIG. 9B. Itshould be noted that, in some embodiments, step 1003 is performed toimprove ball strength throughout the ball pattern, rather than only inthe corner regions. The modified ball pattern 900B may still includeempty intersections, as exemplarily illustrated at 325 e in FIG. 9B.

At step 1005, the semiconductor device is manufactured with the modifiedball pattern 900B which as noted above may still include emptyintersections. Any manufacturing process suitable for fabrication ofsemiconductor devices is applicable. An exemplary process has beendescribed with respect to FIGS. 7A-7B.

FIGS. 11A and 11B are schematic plan views of a ball pattern 1100A and amodified ball pattern 1100B in accordance with some embodiments,respectively. FIG. 12 is a flow chart of a method 1200 in accordancewith some embodiments. The ball patterns of FIGS. 11A-11B will be usedfor illustration purposes in the description of FIG. 12.

At step 1201, a ball pattern (such as the ball pattern 1100A in FIG.11A) of a plurality of connection balls 306 to be formed as electricalconnections for a semiconductor device is received. The connection balls306 are arranged at some, but not all, intersections of the columns androws (not numbered) of the ball pattern 1100A. Thus, some intersectionsremain empty as exemplarily illustrated at 325 e in FIG. 11A.

As step 1203, every empty intersections in the ball pattern 1100A isprovided with a dummy ball 306 d so as to provide a modified ballpattern 1100B with a uniform ball distribution. The modified ballpattern 1100B includes no empty intersections.

In some embodiments, a step 1202 for analyzing the received ball pattern1100A to identify isolated balls is performed before step 1203, in amanner similar to that described with respect to step 802.

At step 1205, the semiconductor device is manufactured with the modifiedball pattern 1100B which as noted above includes no empty intersections.Any manufacturing process suitable for fabrication of semiconductordevices is applicable. An exemplary process has been described withrespect to FIGS. 7A-7B.

FIG. 13 is a schematic cross-section view of a chip scale package (CSP)1300 in accordance with some embodiments. The CSP 1300 includes a chipor die 102 connected to a first side 116 of a substrate 104 by solderbumps 106 arranged on a surface 114, e.g., an active surface, of thechip 102. An encapsulant 108 is formed over the first side 116 of thesubstrate 104 to encapsulate the chip 102 therein. Solder balls 110 areformed on the second, opposite side 118 of the substrate 104 forelectrical connection to other components (not shown).

In the CSP 1300, the ball pattern of the solder bumps 106 and/or thesolder balls 110 has been modified in any of the manner describedherein. Since the ball strength of the CSP 1300 has been improved, anunderfill material is omitted in some embodiments, thereby lowering themanufacturing cost and time while ensuring acceptable ball strength. Infurther embodiments, the CSP 1300 is still provided with an underfillmaterial between the chip 102 and the substrate 104, which furtherincreases the improved ball strength against defects such as warpage,ball crack, die chipping, etc.

Although exemplary embodiments have been described mainly for CSPs,especially wafer-level CSPs, further embodiments are applicable forvarious ball grid array packages as well.

The above method embodiments show exemplary steps, but they are notnecessarily required to be performed in the order shown. Steps is, insome embodiments, added, replaced, changed order, and/or eliminated asappropriate, in accordance with the spirit and scope of embodiments ofthe disclosure. Embodiments that combine different features and/ordifferent embodiments are within scope of the disclosure and will beapparent to those skilled in the art after reviewing this disclosure.

According to some embodiments, a semiconductor device includes a contactregion over a substrate. The semiconductor device further includes ametal pad over the contact region. Additionally, the semiconductordevice includes a post passivation interconnect (PPI) line over themetal pad, where the PPI line is in contact with the metal pad.Furthermore, the semiconductor device includes an under-bump-metallurgy(UBM) layer over the PPI line. Moreover, the semiconductor deviceincludes a plurality of solder balls over the UBM layer, the pluralityof solder balls being arranged at some, but not all, intersections of anumber of columns and rows of a ball pattern.

According to some embodiments, a semiconductor device includes a contactregion over a substrate. Additionally, the semiconductor device includesa metal pad over the contact region, where the metal pad is in contactwith the contact region. Furthermore, the semiconductor device includesa post passivation interconnect (PPI) line over the metal pad. Thesemiconductor device further includes a polymer layer over the PPI line.Additionally, the semiconductor device includes an under-bump-metallurgy(UBM) layer over the polymer layer. Moreover, the semiconductor deviceincludes a plurality of solder balls over the UBM layer, the pluralityof solder balls being arranged at some, but not all, intersections of anumber of columns and rows of a ball pattern, wherein, at least incorner regions of the chip, each solder ball among the plurality ofsolder balls has at least two neighboring solder balls among theplurality of solder balls.

According to some embodiments, a semiconductor device with improved ballstrength includes a chip having an active surface. Furthermore, thesemiconductor device includes a plurality of connection balls on theactive surface and in electrical connection with the chip, saidconnection balls being arranged at some, but not all, intersections of anumber of columns and rows of a ball pattern. Additionally, thesemiconductor device includes a plurality of dummy balls on the activesurface but not in electrical connection with the chip, said dummy ballsbeing arranged at intersections where the connection balls are notarranged, where, at least in corner regions of the chip, everyconnection ball of the plurality of connection balls or dummy ball ofthe plurality of dummy balls has at least two neighboring connectionballs or dummy balls.

It will be readily seen by one of ordinary skill in the art that one ormore of the disclosed embodiments fulfill one or more of the advantagesset forth above. After reading the foregoing specification, one ofordinary skill will be able to affect various changes, substitutions ofequivalents and various other embodiments as broadly disclosed herein.It is therefore intended that the protection granted hereon be limitedonly by the definition contained in the appended claims and equivalentsthereof.

What is claimed is:
 1. A semiconductor device, comprising: a contactregion over a substrate; a metal pad over the contact region; a postpassivation interconnect (PPI) line over the metal pad, wherein the PPIline is in contact with the metal pad; an under-bump-metallurgy (UBM)layer over the PPI line; and a plurality of solder balls over the UBMlayer, the plurality of solder balls being arranged at some, but notall, intersections of a number of columns and rows of a ball pattern. 2.The semiconductor device of claim 1, wherein the plurality of solderballs comprises at least one connection ball and at least one dummyball.
 3. The semiconductor device of claim 1, wherein the columns andthe rows are perpendicular to each other.
 4. The semiconductor device ofclaim 1, wherein the ball pattern is free of any isolated balls, whereinan isolated ball is a ball having at most one ball in an adjacentintersection of the columns and rows.
 5. The semiconductor device ofclaim 1, wherein an intersection of the columns and rows in a corner ofthe ball pattern is free of any solder ball of the plurality of solderballs.
 6. The semiconductor device of claim 1, further comprising a seedlayer between the PPI layer and the UBM layer, wherein the seed layercomprises at least one of aluminum, copper alloy, silver, or gold. 7.The semiconductor device of claim 1, further comprising an adhesivelayer between the PPI layer and the UBM layer, wherein the adhesivelayer comprises at least one of titanium, titanium nitride, tantalum, ortantalum nitride.
 8. A semiconductor device, comprising: a contactregion over a substrate; a metal pad over the contact region, whereinthe metal pad is in contact with the contact region; a post passivationinterconnect (PPI) line over the metal pad; a polymer layer over the PPIline; an under-bump-metallurgy (UBM) layer over the polymer layer; and aplurality of solder balls over the UBM layer, the plurality of solderballs being arranged at some, but not all, intersections of a number ofcolumns and rows of a ball pattern, wherein, at least in corner regionsof the chip, each solder ball among the plurality of solder balls has atleast two neighboring solder balls among the plurality of solder balls.9. The semiconductor device of claim 8, wherein at least one solder ballof the at least two neighboring solder balls is either in the same rowor column of the each solder ball among the plurality of solder balls.10. The semiconductor device of claim 8, wherein the PPI line has athickness less than 30 micrometers (μm).
 11. The semiconductor device ofclaim 8, wherein the ball pattern is free of any isolated balls, whereinan isolated ball is a ball having at most one ball in an adjacentintersection of the columns and rows.
 12. The semiconductor device ofclaim 8, wherein an intersection of the columns and rows in a corner ofthe ball pattern is free of any solder ball of the plurality of solderballs.
 13. The semiconductor device of claim 8, further comprising aseed layer between the PPI layer and the UBM layer, wherein the seedlayer comprises at least one of aluminum, copper alloy, silver, or gold.14. The semiconductor device of claim 8 wherein, the polymer layercomprises epoxy, polyimide, benzocyclobutene (BCB), polybenzoxazole(PBO), or polyimide.
 15. The semiconductor device of claim 8, furthercomprising an adhesive layer between the PPI layer and the UBM layer,wherein the adhesive layer comprises at least one of titanium, titaniumnitride, tantalum, or tantalum nitride.
 16. The semiconductor device ofclaim 8, wherein the plurality of solder balls comprises at least oneconnection ball and at least one dummy ball.
 17. The semiconductordevice of claim 8, wherein the columns and the rows are perpendicular toeach other.
 18. A semiconductor device with improved ball strength, saidsemiconductor device comprising: a chip having an active surface; aplurality of connection balls on the active surface and in electricalconnection with the chip, said connection balls being arranged at some,but not all, intersections of a number of columns and rows of a ballpattern; and a plurality of dummy balls on the active surface but not inelectrical connection with the chip, said dummy balls being arranged atintersections where the connection balls are not arranged; wherein, atleast in corner regions of the chip, every connection ball of theplurality of connection balls or dummy ball of the plurality of dummyballs has at least two neighboring connection balls or dummy balls. 19.The semiconductor device of claim 18, wherein at least one connectionball of the plurality of connection balls outside in one of the cornerregions of the chip has one or fewer neighboring connection balls. 20.The semiconductor device of claim 18, further comprising: a substratehaving opposite surfaces one of which is mechanically connected to saidchip by said plurality of connection balls and the plurality of dummyballs, and electrically connected to said ship via said plurality ofconnection balls; an encapsulant on said one surface of the substrateand covering the chip and the plurality of connection balls and theplurality of dummy balls; and solder balls on the other surface of thesubstrate and in electrical connection with the corresponding connectionballs of the plurality of connection balls via the substrate.